Toners, for use in printers, copiers, and the like, may be prepared by existing mechanical reduction processes, such as a conventional styrene acrylate copolymer based toner process. In such processes, the copolymer resin may be melt kneaded or extruded with a pigment, pulverized and classified to provide toner particles of the desired volume average particle diameter and size distribution.
As an improvement to the foregoing mechanical reduction process, other processes are known in which toner may be prepared via aggregation as opposed to particle size reduction. For example, in chemical aggregation processes, toner may be formed chemically in situ and may not require known pulverization methods. Chemical aggregation processes typically involve the formation of an emulsion latex of the resin particles, in which particles have a small size of, for example, from about 5 nanometers to about 500 nanometers in diameter, by heating the resin in water, or by making a latex in water using an emulsion polymerization method. A colorant dispersion of a pigment dispersed in water may also be separately formed. The colorant dispersion is added to the emulsion latex mixture, and an aggregating or complexing agent is then added to form aggregated toner particles. The aggregated toner particles are then heated to enable coalescence or fusing, thereby achieving aggregated, fused toner particles.
In a pigment dispersion, in order for the pigment particles to form aggregates with the latex particles, the pigment particles should have a size smaller or at least a size comparable to the latex particles, such as between about 5 and about 300 nanometers in diameter, or between about 5 and about 150 nanometers in diameter. There are several well-known methods in the art to prepare pigment dispersions with a particle size less than about 300 or less than about 150 nanometers in diameter, including, for example, the use of a liquid jet interaction apparatus, such as a microfluidizer, to prepare pigment dispersions for use in ink jet inks. Other examples include the preparation of pigment dispersions using a media mill, a ball mill, or an attritor. However, the media mill and the ball mill are known to generate contaminants from the media-media impaction, and the liquid jet interaction apparatus may be prone to mechanical breakdown as a result of high application pressure.
Rotor-stator type homogenizers have been widely used to prepare emulsions and dispersions. However, the particle size achievable with traditional rotor-stator homogenizers may not be as small as those with media mills or high-pressure homogenizers equipped with homogenizing valves or liquid jet interaction chambers.
Currently, pigment dispersion for manufacturing emulsion aggregation (EA) toner may either be dispersed by a high-energy in-line homogenizers or microfluidizers or purchased from a vendor. The pigment dispersions and wax dispersions are then shipped from the place of manufacture or vendor to toner making facilities. Costs associated with processing and transporting pigment dispersions and wax dispersions may be a major component of the overall EA toner manufacturing cost.
Disclosed herein are pigment and wax dual dispersions that can be prepared in a single pot, referred to herein as a dispersion apparatus. In certain embodiments, the one-pot processes disclosed herein may result in significant cost reductions and process efficiencies for the production of toners and inks. The advantages of using a one-pot homogenization process in a single dispersion apparatus for a pigment and wax dual dispersion preparation may, for example, include the following: (1) elimination of two individual dispersion processes; (2) simplification of the processes; (3) increase in productivity and reduction in production and transportation costs; (4) elimination of the need for wax dispersion and pigment dispersion outsourcing; and (5) maintenance of the same performance of the dual dispersions as each dispersion separately.